Simultaneous Reporting of ACK/NACK and Channel-State Information using PUCCH Format 3 Resources

ABSTRACT

A new uplink control channel capability is introduced to enable a mobile terminal to simultaneously report multiple packet receipt status bits and channel-condition bits. In an example embodiment implemented in a mobile terminal the mobile terminal (first determines that channel-state information and hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlink subframes or a plurality of downlink carriers, or both, are scheduled for transmission in an uplink subframe. The mobile terminal then determines whether the number of the hybrid-ARQ ACK/NACK bits is less than or equal to a threshold number. If so, the mobile terminal transmits both the channel-state information and the hybrid-ARQ ACK/NACK bits in physical control channel resources of the first uplink subframe, on a single carrier. In some embodiments, the number of the hybrid-ARQ ACK/NACK bits considered in the previously summarized technique represents a number of ACK/NACK bits after ACK/NACK bundling

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/499,773, filed 2 Apr. 2012, which is a national stage entry ofinternational patent application serial no. PCT/SE12/50152, filed 14Feb. 2012, and claims the benefit of U.S. Provisional Patent Application61/542,503, filed 3 Oct. 2011.

TECHNICAL FIELD

The present invention relates generally to carrier aggregation in amobile communication system and, more particularly, to an efficient useof resources for the physical uplink control channel in wireless systemsusing carrier aggregation.

BACKGROUND

Carrier aggregation is one of the new features recently developed by themembers of the 3rd-Generation Partnership Project (3GPP) for so-calledLong Term Evolution (LTE) systems, and is standardized as part of LTERelease 10, which is also known as LTE-Advanced. An earlier version ofthe LTE standards, LTE Release 8, supports bandwidths up to 20 MHz. InLTE-Advanced, bandwidths up to 100 MHz are supported. The very high datarates contemplated for LTE-Advanced will require an expansion of thetransmission bandwidth. In order to maintain backward compatibility withLTE Release 8 mobile terminals, the available spectrum is divided intoRelease 8-compatible chunks called component carriers. Carrieraggregation enables bandwidth expansion beyond the limits of LTE Release8 systems by allowing mobile terminals to transmit data over multiplecomponent carriers, which together can cover up to 100 MHz of spectrum.Importantly, the carrier aggregation approach ensures compatibility withearlier Release 8 mobile terminals, while also ensuring efficient use ofa wide carrier by making it possible for legacy mobile terminals to bescheduled in all parts of the wideband LTE-Advanced carrier.

The number of aggregated component carriers, as well as the bandwidth ofthe individual component carrier, may be different for uplink (UL) anddownlink (DL) transmissions. A carrier configuration is referred to as“symmetric” when the number of component carriers in each of thedownlink and the uplink are the same. In an asymmetric configuration, onthe other hand, the numbers of component carriers differ between thedownlink and uplink. The number of component carriers configured for ageographic cell area may be different from the number of componentcarriers seen by a given mobile terminal. A mobile terminal, forexample, may support more downlink component carriers than uplinkcomponent carriers, even though the same number of uplink and downlinkcomponent carriers may be offered by the network in a particular area.

LTE systems can operate in either Frequency-Division Duplex (FDD) modeor Time-Division Duplex (TDD) mode. In FDD mode, downlink and uplinktransmissions take place in different, sufficiently separated, frequencybands. In TDD mode, on the other hand, downlink and uplink transmissiontake place in different, non-overlapping time slots. Thus, TDD canoperate in unpaired spectrum, whereas FDD requires paired spectrum. TDDmode also allows for different asymmetries in terms of the amount ofresources allocated for uplink and downlink transmission, respectively,by means of different downlink/uplink configurations. These differingconfigurations permit the shared frequency resources to be allocated todownlink and uplink use in differing proportions. Accordingly, uplinkand downlink resources can be allocated asymmetrically for a given TDDcarrier.

One consideration for carrier aggregation is how to transmit controlsignaling from the mobile terminal on the uplink to the wirelessnetwork. Uplink control signaling may include acknowledgement (ACK) andnegative-acknowledgement (NACK) signaling for hybrid automatic repeatrequest (Hybrid ARQ, or HARQ) protocols, channel state information (CSI)and channel quality information (CQI) reporting for downlink scheduling,and scheduling requests (SRs) indicating that the mobile terminal needsuplink resources for uplink data transmissions. In the carrieraggregation context, one solution would be to transmit the uplinkcontrol information on multiple uplink component carriers associatedwith different downlink component carriers. However, this option islikely to result in higher mobile terminal power consumption and adependency on specific mobile terminal capabilities. Accordingly,improved techniques are needed for managing the transmission of uplinkcontrol-channel information in systems that employ carrier aggregation.

SUMMARY

Even with the several uplink control channel techniques and formatsalready standardized by 3GPP, problems remain. For instance, an LTEmobile terminal operating in TDD mode and configured with ACK/NACKmultiplexing cannot simultaneously report multiple ACK/NACK bits and aperiodic CSI report. If such a collision happens, the conventionalapproach is to simply drop the CSI report, and transmit only theACK/NACK bits. This behavior is independent of whether the multipleACK/NACK bits stem from multiple subframes or multiple aggregated cells.

Periodic CSI reports for multiple cells are handled in Release 10 withtime-shifted reporting times, to minimize collisions among CSI reports.To maintain roughly the same CSI periodicity per cell, it is obviousthat periodic CSI reports are transmitted more frequently than inRelease 8 systems. In each subframe without PUSCH transmission whereperiodic CSI and multi-cell ACK/NACK collide, the periodic CSI aredropped. Since CSI reports are required for link adaptation, reduced CSIfeedback degrades downlink performance. This is in particular a problemfor TDD, where only a minority of the available subframes may be uplinksubframes.

Thus, without changes to current 3GPP specifications, collisions betweenACK/NACK transmissions and CSI reports will likely lead to dropped CSIreports. The novel techniques described herein enable simultaneoustransmission of multiple ACK/NACK bits and CSI. With the use of thesetechniques, fewer CSI reports are dropped, which improves linkadaptation and increases throughput. More particularly, in severalembodiments of the present invention, these problems are addressed byintroducing a new uplink control channel capability that enables amobile terminal to simultaneously report to the radio network multiplepacket receipt status bits, (e.g., ACK/NACK bits) and channel-conditionbits (e.g., CSI reports). In some embodiments, this uplink controlchannel capability also supports sending uplink scheduling requests fromthe UE in addition to transmitting multiple packet receipt status bitsand channel-condition bits. In several embodiments, if the mobileterminal does not have any channel-condition bits to report in a givensubframe, it may transmit ACK/NACK bits using an uplink control channeltransmission mode that does not allow such simultaneous transmission.

In an example embodiment implemented in a mobile terminal, the mobileterminal first determines that channel-state information and hybrid-ARQACK/NACK bits corresponding to a plurality of downlink subframes or aplurality of downlink carriers, or both, are scheduled for transmissionin an uplink subframe. The mobile terminal then determines whether thenumber of the hybrid-ARQ ACK/NACK bits is less than or equal to athreshold number. If so, the mobile terminal transmits both thechannel-state information and the hybrid-ARQ ACK/NACK bits in physicalcontrol channel resources of the uplink subframe, on a single carrier.In some embodiments, the number of the hybrid-ARQ ACK/NACK bitsconsidered in the previously summarized technique represents a number ofACK/NACK bits after ACK/NACK bundling. In some embodiments, thethreshold number depends on the number of channel-state information bitsscheduled for transmission in the uplink subframe.

In a variant of these techniques, the mobile terminal determines, for adifferent uplink subframe, that second channel-state information andsecond hybrid-ARQ ACK/NACK bits corresponding to a plurality of downlinksubframes or a plurality of downlink carriers, or both, are scheduledfor transmission. The mobile terminal again determines whether thenumber of the second hybrid-ARQ ACK/NACK bits is less than or equal tothe threshold number. In this case, the answer is no, so the mobileterminal drops the second channel-state information and transmits thesecond hybrid-ARQ ACK/NACK bits in physical control channel resources ofthe second uplink subframe, on a single carrier, in response todetermining that the number of hybrid-ARQ ACK/NACK bits to betransmitted in the second uplink subframe is not less than or equal tothe threshold number.

In another variant, the mobile terminal determines, for a differentuplink subframe, that second channel-state information and a secondhybrid-ARQ ACK/NACK bits corresponding to a plurality of downlinksubframes or a plurality of downlink carriers, or both, are scheduledfor transmission in a second uplink subframe. The mobile terminal againdetermines whether the number of the second hybrid-ARQ ACK/NACK bits isless than or equal to the threshold number. If not, the mobile terminalbundles the second hybrid-ARQ ACK/NACK bits to produce a number ofbundled ACK/NACK bits that is less than or equal to the thresholdnumber, in response to determining that the number of hybrid-ARQACK/NACK bits to be transmitted in the second uplink subframe is notless than or equal to the threshold number, and transmits both thesecond channel-state information and the bundled ACK/NACK bits inphysical control channel resources of the second uplink subframe, on asingle carrier.

As discussed more fully below, the present techniques may be implementedin a Long-Term Evolution (LTE) wireless system, in which case thehybrid-ARQ ACK/NACK bits and the channel-state information aretransmitted using a Physical Uplink Control Channel (PUCCH) Format 3resource. In some embodiments, the mobile terminal encodes thehybrid-ARQ ACK/NACK bits using a first encoder and separately encodesthe channel-state information bits using a second encoder, andinterleaves the encoded hybrid-ARQ ACK/NACK bits and the encodedchannel-state information bits before transmission.

Complementary techniques for receiving and processing informationtransmitted according to the techniques described above are alsodisclosed in detail below. In addition, mobile terminal apparatus andbase station apparatus adapted to carry out any of these techniques aredisclosed. Of course, the present invention is not limited to theabove-summarized features and advantages. Indeed, those skilled in theart will recognize additional features and advantages upon reading thefollowing detailed description, and upon viewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a mobile communication system.

FIG. 2 illustrates a grid of time-frequency resources for a mobilecommunication system that uses OFDM.

FIG. 3 illustrates the time-domain structure of an LTE signal.

FIG. 4 illustrates the positioning of PUCCH resources in an uplinksubframe according to Release 8 standards for LTE.

FIG. 5 illustrates the encoding and modulation of channel-statusinformation according to PUCCH Format 2.

FIG. 6 illustrates several carriers aggregated to form an aggregatedbandwidth of 100 MHz.

FIGS. 7, 8, and 9 illustrate the coding of multiple ACK/NACK bits usingchannel selection.

FIG. 10 illustrates the encoding and modulation of multiple ACK/NACKbits according to PUCCH Format 3.

FIGS. 11, 12, 13 are process flow diagrams illustrating example methodsfor simultaneous reporting of channel-state information and hybrid-ARQACK/NACK information.

FIG. 14 is a process flow diagram illustrating an example method forreceiving and decoding simultaneously reported channel-state informationand hybrid-ARQ ACK/NACK bits.

FIG. 15 is a block diagram illustrating components of an examplecommunications node according to some embodiments of the invention.

FIG. 16 illustrates functional components of an example mobile terminal.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates an exemplary mobilecommunication network 10 for providing wireless communication servicesto mobile terminals 100. Three mobile terminals 100, which are referredto as “user equipment” or “UE” in LTE terminology, are shown in FIG. 1.The mobile terminals 100 may comprise, for example, cellular telephones,personal digital assistants, smart phones, laptop computers, handheldcomputers, or other devices with wireless communication capabilities.The mobile communication network 10 comprises a plurality of geographiccell areas or sectors 12. Each geographic cell area or sector 12 isserved by a base station 20, which is referred to in LTE as a NodeB orEvolved NodeB (eNodeB). One base station 20 may provide service inmultiple geographic cell areas or sectors 12. The mobile terminals 100receive signals from base station 20 on one or more downlink (DL)channels, and transmit signals to the base station 20 on one or moreuplink (UL) channels.

For illustrative purposes, several embodiments of the present inventionwill be described in the context of a Long-Term Evolution (LTE) system.Those skilled in the art will appreciate, however, that severalembodiments of the present invention may be more generally applicable toother wireless communication systems, including, for example, WiMax(IEEE 802.16) systems.

LTE uses Orthogonal Frequency Division Multiplexing (OFDM) in thedownlink and Discrete Fourier Transform (DFT)-spread OFDM in the uplink.The basic LTE downlink physical resource can be viewed as atime-frequency grid. FIG. 2 illustrates a portion of the availablespectrum of an exemplary OFDM time-frequency grid 50 for LTE. Generallyspeaking, the time-frequency grid 50 is divided into one millisecondsubframes. Each subframe includes a number of OFDM symbols. For a normalcyclic prefix (CP) length, suitable for use in situations wheremultipath dispersion is not expected to be extremely severe, a subframeconsists of fourteen OFDM symbols. A subframe has only twelve OFDMsymbols if an extended cyclic prefix is used. In the frequency domain,the physical resources are divided into adjacent subcarriers with aspacing of 15 kHz. The number of subcarriers varies according to theallocated system bandwidth. The smallest element of the time-frequencygrid 50 is a resource element. A resource element consists of one OFDMsubcarrier during one OFDM symbol interval.

Resource elements are grouped into resource blocks, where each resourceblock in turn consists of twelve OFDM subcarriers, within one of twoequal-length slots of a subframe. FIG. 2 illustrates a resource blockpair, comprising a total of 168 resource elements.

Downlink transmissions are dynamically scheduled, in that in eachsubframe the base station transmits control information identifying themobile terminals to which data is transmitted and the resource blocks inwhich that data is transmitted, for the current downlink subframe. Thiscontrol signaling is typically transmitted in a control region, whichoccupies the first one, two, three, or four OFDM symbols in eachsubframe. A downlink system with a control region of three OFDM symbolsis illustrated in FIG. 2. The dynamic scheduling information iscommunicated to the UEs (“user equipment,” 3GPP terminology for a mobilestation) via a Physical Downlink Control Channel (PDCCH) transmitted inthe control region. After successful decoding of a PDCCH, the UEperforms reception of traffic data from the Physical Downlink SharedChannel (PDSCH) or transmission of traffic data on the Physical UplinkShared Channel (PUSCH), according to pre-determined timing specified inthe LTE specifications.

As shown in FIG. 3, LTE downlink transmissions are further organizedinto radio frames of 10 milliseconds, in the time domain, each radioframe consisting of ten subframes. Each subframe can further be dividedinto two slots of 0.5 milliseconds duration. Furthermore, resourceallocations in LTE are often described in terms of resource blocks,where a resource block corresponds to one slot (0.5 ms) in the timedomain and twelve contiguous subcarriers in the frequency domain.Resource blocks are numbered in the frequency domain, starting with 0from one end of the system bandwidth.

For error control, LTE uses hybrid-ARQ (HARQ), where, after receivingdownlink data in a subframe, the mobile terminal attempts to decode itand reports to the base station whether the decoding was successful(ACK) or not (NACK) via a Physical Uplink Control Channel (PUCCH). Inthe event of an unsuccessful decoding attempt, the base station (evolvedNodeB, or eNodeB, in 3GPP terminology) can retransmit the erroneousdata. Similarly, the base station can indicate to the UE whether thedecoding of the PUSCH was successful (ACK) or not (NACK) via thePhysical Hybrid ARQ Indicator CHannel (PHICH).

In addition to the hybrid-ARQ ACK/NACK information transmitted from themobile terminal to the base station, uplink control signaling from themobile terminal to the base station also includes reports related to thedownlink channel conditions, referred to generally as channel-stateinformation (CSI) or channel-quality information (CQI). This CSI/CQI isused by the base station to assist in downlink resource schedulingdecisions. Because LTE systems rely on dynamic scheduling of bothdownlink and uplink resources, uplink control-channel information alsoincludes scheduling requests, which the mobile terminal sends toindicate that it needs uplink traffic-channel resources for uplink datatransmissions.

When a UE has data to transmit on PUSCH, it multiplexes the uplinkcontrol information with data on PUSCH. Thus, a UE only uses PUCCH forsignaling this uplink control information when it does not have any datato transmit on PUSCH. Accordingly, if the mobile terminal has not beenassigned an uplink resource for data transmission, Layer 1/Layer 2(L1/L2) control information, including channel-status reports,hybrid-ARQ acknowledgments, and scheduling requests, is transmitted inuplink resources (resource blocks) specifically assigned for uplinkL1/L2 control on the Physical Uplink Control CHannel (PUCCH), which wasfirst defined in Release 8 of the 3GPP specifications (LTE Rel-8).

As illustrated in FIG. 4, these resources are located at the edges ofthe uplink cell bandwidth that is available to the mobile terminal foruse. Each physical control channel resource is made up of a pair ofresource blocks, where each resource block in turn consists of twelveOFDM subcarriers, within one of the two slots of the uplink subframe. Inorder to provide frequency diversity, the physical control channelresources are frequency hopped on the slot boundary—thus, the firstresource block of the pair is at the lower part of the spectrum withinthe first slot of the subframe while the second resource block of thepair is positioned at the upper part of the spectrum during the secondslot of the subframe (or vice-versa). If more resources are needed forthe uplink L1/L2 control signaling, such as in case of very largeoverall transmission bandwidth supporting a large number of users,additional resource blocks can be assigned, adjacent to the previouslyassigned resource blocks.

The reasons for locating the PUCCH resources at the edges of the overallavailable spectrum are two-fold. First, together with the frequencyhopping described above, this maximizes the frequency diversityexperienced by the control signaling, which can be encoded so that it isspread across both resource blocks. Second, assigning uplink resourcesfor the PUCCH at other positions within the spectrum, i.e., not at theedges, would fragment the uplink spectrum, making it difficult to assignvery wide transmission bandwidths to a single mobile terminal whilestill retaining the single-carrier property of the uplink transmission.

When a UE has ACK/NACK to send in response to a downlink PDSCHtransmission, it determines which PUCCH resource to use from the PDCCHtransmission that assigned the PDSCH resources to the UE. Morespecifically, an index to the PUCCH resource for the UE is derived fromthe number of the first control channel element used to transmit thedownlink resource assignment. When a UE has a scheduling request or CQIto send, it uses a specific PUCCH resource that has been pre-configuredfor the UE by higher layer signaling.

Depending on the different types of information that PUCCH is to carry,several different PUCCH formats may be used. The data-carrying capacityof a pair of resource blocks during one subframe is more than isgenerally needed for the short-term control signaling needs of onemobile terminal. Therefore, to efficiently exploit the resources setaside for control signaling, multiple mobile terminals can share thesame physical control channel resource. This is done by assigning eachof several mobile terminals different orthogonal phase-rotations of acell-specific, length-12, frequency-domain sequence and/or differentorthogonal time-domain cover codes. By applying these frequency-domainrotations and/or time-domain covering codes to the encoded controlchannel data, as many as 36 mobile terminals can share a given physicalcontrol channel resource in some circumstances.

Several different encoding formats have been developed by 3GPP to encodedifferent quantities and types of uplink control channel data, withinthe constraints of a single physical control channel resource. Theseseveral formats, known generally as PUCCH Format 1, PUCCH Format 2, andPUCCH Format 3, are described in detail at pages 226-242 of the text “4GLTE/LTE-Advanced for Mobile Broadband,” by Erik Dahlman, StefanParkvall, and Johan Skold (Academic Press, Oxford UK, 2011), and aresummarized briefly below.

PUCCH formats 1, 1a, and 1b, which are used to transmit schedulingrequests and/or ACK/NACK, are based on cyclic shifts of a Zadoff-Chusequence. A modulated data symbol is multiplied with the cyclicallyZadoff-Chu shifted sequence. The cyclic shift varies from one symbol toanother and from one slot to the next. Although twelve different shiftsare available, higher-layer signaling may configure UEs in a given cellto use fewer than all of the shifts, to maintain orthogonality betweenPUCCH transmissions in cells that exhibit high frequency selectivity.After the modulated data symbol is multiplied with the Zadoff-Chusequence, the result is spread using an orthogonal spreading sequence.PUCCH formats 1, 1a, and 1b carry three reference symbols per slot (whennormal cyclic prefix is used), at SC-FDMA symbol numbers 2, 3, and 4.

PUCCH Formats 1a and 1b refer to PUCCH transmissions that carry eitherone or two hybrid-ARQ acknowledgements, respectively. A PUCCH Format 1transmission (carrying only a SR) is transmitted on a UE-specificphysical control channel resource (defined by a particulartime-frequency resource, a cyclic-shift, and an orthogonal spreadingcode) that has been pre-configured by RRC signaling. Likewise, PUCCHFormat 1a or 1b transmissions carrying only hybrid-ARQ acknowledgementsare transmitted on a different UE-specific physical control channelresource. PUCCH Format 1a or 1b transmissions that are intended to carryboth ACK/NACK information and a scheduling request are transmitted onthe assigned SR resource for positive SR transmission, and are encodedwith the ACK/NACK information.

PUCCH Format 1/1a/1b transmissions carry only one or two bits ofinformation (plus scheduling requests, depending on the physical controlchannel resource used for the transmission). Because channel-stateinformation reports require more than two bits of data per subframe,PUCCH Format 2/2a/2b is used for these transmissions. As illustrated inFIG. 5, in PUCCH formats 2, 2a, and 2b, the channel-status reports arefirst block-coded, and then the block-coded bits for transmission arescrambled and QPSK modulated. (FIG. 5 illustrates coding for a subframeusing a normal cyclic prefix, with seven symbols per slot. Slots usingextended cyclic prefix have only one reference-signal symbol per slot,instead of two.) The resulting ten QPSK symbols are then multiplied witha cyclically shifted Zadoff-Chu type sequence, a length-12 phase-rotatedsequence, where again the cyclic shift varies between symbols and slots.Five of the symbols are processed and transmitted in the first slot,i.e., the slot appearing on the left-hand side of FIG. 5, while theremaining five symbols are transmitted in the second slot. PUCCH formats2, 2a, and 2b carry two reference symbols per slot, located on SC-FDMAsymbol numbers 1 and 5.

For UEs operating in accordance with LTE Release 8 or LTE Release 9(i.e., without carrier aggregation), it is possible to configure the UEin a mode where it reports ACK/NACK bits and CSI bits simultaneously. Ifthe UE is using normal cyclic prefix, one or two ACK/NACK bits aremodulated onto a QPSK symbol on the second reference signal (RS)resource element in each slot of the PUCCH format 2. If one ACK/NACK bitis modulated on the second RS in each slot, the PUCCH format used by theUE is referred to as PUCCH Format 2a. If two ACK/NACK bits are modulatedon the second RS in each slot the PUCCH format used by the UE isreferred to as PUCCH Format 2b. If the UE is configured with extendedcyclic prefix, one or two ACK/NACK bits are jointly coded withchannel-state information (CSI) feedback and transmitted together withinPUCCH format 2.

As with PUCCH Format 1 transmissions, a pair of resource blocksallocated to PUCCH can carry multiple PUCCH Format 2 transmissions fromseveral UEs, with the separate transmissions separated by the cyclicshifting. As with PUCCH Format 1, each unique PUCCH Format 2 resourcecan be represented by an index from which the phase rotation and otherquantities necessary are derived. The PUCCH format 2 resources aresemi-statically configured. It should be noted that a pair of resourceblocks can either be configured to support a mix of PUCCH formats2/2a/2b and 1/1a/1b, or to support formats 2/2a/2b exclusively.

3GPP's Release 10 of the LTE standards (LTE Release 10) has beenpublished and provides support for bandwidths larger than 20 MHz,through the use of carrier aggregation. One important requirement placedon the development of LTE Release 10 specifications was to assurebackwards compatibility with LTE Release 8. The need for spectrumcompatibility dictated that an LTE Release 10 carrier that is wider than20 MHz should appear as a number of distinct, smaller bandwidth, LTEcarriers to an LTE Release 8 mobile terminal. Each of these distinctcarriers can be referred to as a component carrier.

For early LTE Release 10 system deployments in particular, it can beexpected that there will be a relatively small number of LTE Release10-capable mobile terminals, compared to many “legacy” mobile terminalsthat conform to earlier releases of the LTE specifications. Therefore,it is necessary to ensure the efficient use of wide carriers for legacymobile terminals as well as Release 10 mobile terminals, i.e., that itis possible to implement carriers where legacy mobile terminals can bescheduled in all parts of the wideband LTE Release 10 carrier.

One straightforward way to obtain this is by means of a technique calledcarrier aggregation. With carrier aggregation, an LTE Release 10 mobileterminal can receive multiple component carriers, where each componentcarrier has (or at least may have) the same structure as a Release 8carrier. The basic concept of carrier aggregation is illustrated in FIG.6, which illustrates the aggregation of five 20-MHz component carriersto yield an aggregated bandwidth of 100 MHz.

The number of aggregated component carriers as well as the bandwidth foreach individual component carrier may be different for uplink anddownlink. In a symmetric configuration, the number of component carriersin downlink and uplink is the same, whereas the numbers of uplink anddownlink carriers differ in an asymmetric configuration.

During initial access, an LTE Release 10 mobile terminal behavessimilarly to an LTE Release 8 mobile terminal, requesting and obtainingaccess to a single carrier for the uplink and downlink. Upon successfulconnection to the network a mobile terminal may—depending on its owncapabilities and the network—be configured with additional componentcarriers in the uplink (UL) and downlink (DL).

Even if a mobile terminal is configured with additional componentcarriers, it need not necessarily monitor all of them, all of the time.This is because LTE Release 10 supports activation of componentcarriers, as distinct from configuration. The mobile terminal monitorsfor PDCCH and PDSCH only component carriers that are both configured andactivated. Since activation is based on Medium Access Control (MAC)control elements—which are faster than RRC signaling—theactivation/de-activation process can dynamically follow the number ofcomponent carriers that is required to fulfill the current data rateneeds. All but one component carrier—the downlink Primary componentcarrier (DL PCC)—can be deactivated at any given time.

Scheduling of a component carrier is done using the PDCCH or ePDCCH(extended PDCCH), via downlink assignments. Control information on thePDCCH or ePDCCH is formatted as a Downlink Control Information (DCI)message. In Release 8, where a mobile terminal only operates with onedownlink and one uplink component carrier, the association betweendownlink assignment, uplink grants, and the corresponding downlink anduplink component carriers is very clear. In Release 10, however, twomodes of carrier aggregation need to be distinguished. The first mode isvery similar to the operation of multiple Release 8 mobile terminals, inthat a downlink assignment or uplink grant contained in a DCI messagetransmitted on a component carrier applies either to the downlinkcomponent carrier itself or to a uniquely associated uplink componentcarrier. (This association may be either via cell-specific orUE-specific linking.) A second mode of operation augments a DCI messagewith a Carrier Indicator Field (CIF). A DCI containing a downlinkassignment with CIF applies to the specific downlink component carrierindicated by the CIF, while a DCI containing an uplink grant with CIFapplies to the indicated uplink component carrier.

DCI messages for downlink assignments contain, among other things,resource block assignment, modulation and coding scheme relatedparameters, and HARQ redundancy version indicators. In addition to thoseparameters that relate to the actual downlink transmission, most DCIformats for downlink assignments also contain a bit field for TransmitPower Control (TPC) commands. These TPC commands are used to control theuplink power control behavior of the corresponding PUCCH that is used totransmit the HARQ feedback.

Transmission of PUCCH in a carrier aggregation scenario (called “CAPUCCH” hereinafter) creates several issues. In particular, multiplehybrid-ARQ acknowledgement bits need to be fed back in the event ofsimultaneous transmission on multiple component carriers. Furthermore,from the perspective of the UE, both symmetric and asymmetricuplink/downlink component carrier configurations are supported. For someconfigurations, one may consider the possibility to transmit uplinkcontrol information on multiple PUCCH, or on multiple uplink componentcarriers. However, this option is likely to result in higher UE powerconsumption and a dependency on specific UE capabilities. It may alsocreate implementation issues due to inter-modulation products, and wouldlead to generally higher complexity for implementation and testing.

Therefore, the transmission of PUCCH should have limited dependency onthe uplink/downlink component carrier configuration. Thus, all uplinkcontrol information for a UE is transmitted on a single uplink componentcarrier, according to the 3GPP Release 10 specifications. Asemi-statically configured and UE-specific uplink primary componentcarrier, which is frequently referred to as the “anchor carrier,” isexclusively used for PUCCH.

UEs operating in accordance with LTE Release 8 or LTE Release 9 (i.e.,without carrier aggregation) are configured with only a single downlinkcomponent carrier and uplink component carrier. The time-frequencyresource location of the first Control Channel Element (CCE) used totransmit PDCCH for a particular downlink assignment determines thedynamic ACK/NACK resource for Release 8 PUCCH. No PUCCH collisions canoccur, since all PDCCH for a given subframe are transmitted using adifferent first CCE.

In a cell-asymmetric carrier aggregation scenario (or perhaps also forother reasons), multiple downlink component carriers may becell-specifically linked to the same uplink component carrier. Mobileterminals configured with the same uplink component carrier but withdifferent downlink component carriers (with any of the downlinkcomponent carrier that are cell-specifically linked with the uplinkcomponent carrier) share the same uplink PCC but may have differentaggregations of secondary component carriers, in either the uplink ordownlink. In this case, mobile terminals receiving their downlinkassignments from different downlink component carriers will transmittheir HARQ feedback on the same uplink component carrier. It is up tothe scheduling process at the base station (in LTE, the evolved Node B,or eNB) to ensure that no PUCCH collisions occur.

When a mobile terminal is configured with multiple downlink componentcarriers it makes sense to use the Release 8 approach when possible.Each PDCCH transmitted on the downlink primary component carrier has,according to Release 8 specifications, a PUCCH resource reserved on theuplink primary component carrier. Thus, when a mobile terminal isconfigured with multiple downlink component carriers but receives adownlink assignment for only the downlink primary component carrier, itshould still use the PUCCH resource on the uplink primary componentcarrier as specified in Release 8.

An alternative would be to specify the use of a “carrier aggregationPUCCH,” or “CA PUCCH,” which enables feedback of HARQ bits correspondingto the number of configured component carriers, for use whenever themobile terminal is configured with multiple downlink carriers,regardless of whether a particular assignment is only for the downlinkprimary component carrier. Since configuration is a rather slow processand a mobile terminal may be configured with multiple component carriersoften—even though only the downlink primary component carrier is activeand used—this would lead to a very inefficient usage of carrieraggregation PUCCH resources.

Upon reception of downlink assignments on a single secondary componentcarrier or upon reception of multiple downlink assignments, a specialcarrier aggregation PUCCH should be used. While in the latter case it isobvious to use CA PUCCH—since only CA PUCCH supports feedback of HARQbits of multiple component carriers—it is less clear that CA PUCCHshould also be used in the first case. First, a downlink secondarycomponent carrier assignment alone is not typical. The eNodeB schedulershould strive to schedule a single downlink component carrier assignmenton the downlink primary component carrier and try to de-activatesecondary component carriers if only a single downlink carrier isneeded. Another issue is that the PDCCH for a downlink secondarycomponent carrier assignment is transmitted on the secondary componentcarrier (assuming CIF is not configured) and, hence there is noautomatically reserved Rel-8 PUCCH resource on the uplink primarycomponent carrier. Using the Rel-8 PUCCH even for stand-alone downlinksecondary component carrier assignments would require reserving Rel-8resources on the uplink primary component carrier for any downlinkcomponent carrier that is configured for any mobile terminal that usesthis uplink primary component carrier. Since stand-alone secondarycomponent carrier assignments are atypical, this would lead to anunnecessary over-provisioning of Rel-8 PUCCH resources on uplink primarycomponent carrier.

It should be noted that a possible error case that may occur with CAPUCCH arises when the eNodeB schedules a mobile terminal on multipledownlink component carriers, including the primary component carrier. Ifthe mobile terminal misses all but the downlink primary componentcarrier assignment, it will use Rel-8 PUCCH instead of CA PUCCH. Todetect this error case the eNodeB has to monitor both the Rel-8 PUCCHand the CA PUCCH in the event that assignments for multiple downlinkcomponent carriers have been sent.

The number of HARQ feedback bits that a mobile terminal has to providedepends on the number of downlink assignments actually received by themobile terminal. In a first case, the mobile terminal could adopt aparticular CA PUCCH format according to the number of receivedassignments and provide feedback accordingly. However, one or morePDCCHs carrying downlink assignments can get lost. Adopting a CA PUCCHformat according to the number of received downlink assignments istherefore ambiguous, and would require the testing of many differenthypotheses at the eNodeB.

Alternatively, the PUCCH format could be set by the carrier activationmessage. A working group in 3GPP has decided that activation andde-activation of component carriers is done with Medium Access Control(MAC) layer control element and that per-component-carrier activationand de-activation is supported. MAC signaling, and especially the HARQfeedback signaling indicating whether the activation command has beenreceived successfully, is error prone. Furthermore, this approachrequires testing of multiple hypotheses at the eNodeB.

Accordingly, basing the CA PUCCH format on the number of configuredcomponent carrier seems therefore the safest choice. Configuration ofcomponent carrier is based on Radio Resource Control (RRC) signaling.After successful reception and application of a new configuration, aconfirmation message is sent back, making RRC signaling very safe.

As noted earlier, feedback of ARQ ACK/NACK information for two or morecomponent carriers may require the transmission of more than two bits,which is the most that can be handled by PUCCH Format 1. Accordingly,PUCCH for carrier aggregation scenarios requires additional techniquesor formats. Two approaches were specified in LTE Release 10specifications. First, PUCCH Format 1 may be used in combination with atechnique called resource selection or channel selection. However, thisis not an efficient solution for more than four bits. Accordingly,another format, PUCCH Format 3, has been developed to enable thepossibility of transmitting more than four ACK/NACK bits in an efficientway.

The first of these two approaches is often simply called channelselection. The basic principle behind this approach is that the UE isassigned a set of up to four different PUCCH format 1a/1b resources. TheUE then selects one of the resources according to the ACK/NACK sequencethe UE should transmit. Thus, the selection of a particular one of theresources serves to communicate up to two bits of information. On one ofthe assigned resources the UE then transmits a QPSK or BPSK symbolvalue, encoding the remaining one or two bits of information. The eNodeBdetects which resource the UE uses as well as the QPSK or BPSK valuetransmitted on the used resource and combines this information to decodea HARQ response for downlink cells associated with the transmitting UE.

The use of channel selection to code ACK (A), NACK (N) and DTX (D) formultiple component carriers is shown in FIG. 7, FIG. 8, and FIG. 9,which apply to LTE FDD systems. A similar type of mapping, but includinga bundling approach, is done for TDD in the event that the UE isconfigured with channel selection.

In FIG. 7, two ACK/NACK messages are transmitted and two PUCCH resourcesare configured. In each resource, a BPSK modulated symbol can betransmitted, as shown in the figure, hence in total one out of fourdifferent signals can be transmitted. If PUCCH resource 1 is selected,then one of the BPSK constellation points indicates an ACK for primarycell codeword 0 (indicated as PCell CW0 in the figures) and a NACK forsecondary cell codeword 0 (Scell CW0), or ACK and DTX respectively. Thisis shown as A/N and A/D in FIG. 7. The other constellation point in thisPUCCH resource 1 indicates NACK and NACK (or NACK and DTX) for theprimary cell and secondary cell respectively. Thus, a BPSK symboltransmitted in PUCCH resource 1 indicates either ACK/NACK or ACK/DTX forthe primary cell and secondary cell, respectively, for a first value ofthe BPSK symbol, and NACK/NACK or NACK/DTX for the primary cell andsecondary cell, respectively, for the other value of the BPSK symbol. IfPUCCH resource 2 is selected for transmission, on the other hand, thenthe first value of the BPSK symbol indicate A/A (ACK/ACK) for theprimary and secondary cells, respectively, while the second valueindicates N/A (NACK/ACK) or D/A (DTX/ACK) for the primary and secondarycells.

For example, if the mobile terminal wants to report an ACK for theprimary and a NACK for the secondary cell, then PUCCH resource 1 isselected and the BPSK constellation point corresponding to A/N istransmitted. Note that since this constellation point also indicatesA/D, there is no difference from the eNB perspective whether the mobileterminal reports a NACK or DTX for the transmission on the secondarycell. In FIGS. 8 and 9, this principle is extended to 3 and 4 ACK/NACKbits, respectively. Thus, three PUCCH resources are configured to send 3ACK/NACK bits, as shown in FIG. 8, while four PUCCH resources areconfigured to send 4 ACK/NACK bits, as shown in FIG. 9. QPSK modulationis used in both cases; thus a symbol transmitted in a given one of the 3or four PUCCH resources can indicate one of up to four differentcombinations of ACK/NACK bits.

A second approach, which is more efficient when more than four bits ofinformation need to be transmitted, is called PUCCH Format 3 and isbased on Discrete Fourier Transform (DFT)-spread OFDM. FIG. 10 shows ablock diagram of that design, for a single slot. The same processing isapplied to the second slot of the uplink frame. The multiple ACK/NACKbits are encoded, using a forward-error correction (FEC) code, to form48 coded bits. The coded bits are then scrambled, using cell-specific(and possibly DFT-spread OFDM symbol dependent) sequences. 24 bits aretransmitted within the first slot and the other 24 bits are transmittedwithin the second slot. The 24 bits per slot are then mapped into 12QPSK symbols, as indicated by the blocks labeled “QPSK mapping” in FIG.10, which appear in five of the OFDM symbols of the slot (symbols 0, 2,3, 4, and 6). The sequence of symbols in each of these five symbols inthe slot is spread with OFDM-symbol-specific orthogonal cover codes,indicated by OC0, OC1, OC2, OC3, and OC4 in FIG. 10, and cyclicallyshifted, prior to DFT-precoding. The DFT-precoded symbols are convertedto OFDM symbols (using an Inverse Fast-Fourier Transform, or IFFT) andtransmitted within one resource block (the bandwidth resource) and fiveDFT-spread OFDM symbols (the time resource). The spreading sequence ororthogonal cover code (OC) is UE-specific and enables multiplexing of upto five users within the same resource blocks.

For the reference signals (RS), cyclic-shifted constant-amplitudezero-autocorrelation (CAZAC) sequences can be used. For example, thecomputer optimized sequences in 3GPP TS 36.211, “Physical Channels andModulation,” can be used.

Even with the several PUCCH formats already standardized by 3GPP,problems remain. For instance, an LTE mobile terminal operating in TDDmode and configured with ACK/NACK multiplexing cannot simultaneouslyreport multiple ACK/NACK bits and a periodic CSI report. If such acollision happens, the conventional approach is to simply drop the CSIreport, and transmit only the ACK/NACK bits. This behavior isindependent of whether the multiple ACK/NACK bits stem from multiplesubframes or multiple aggregated cells.

Periodic CSI reports for multiple cells are handled in Release 10 withtime-shifted reporting times, to minimize collisions among CSI reports.To maintain roughly the same CSI periodicity per cell, it is obviousthat periodic CSI reports are transmitted more frequently than inRelease 8 systems. In each subframe without PUCCH transmission whereperiodic CSI and multi-cell ACK/NACK collide, the periodic CSI aredropped. Since CSI reports are required for link adaptation, reduced CSIfeedback degrades downlink performance. This is in particular a problemfor TDD, where only a minority of the available subframes may be uplinksubframes.

In several embodiments of the present invention, these problems areaddressed by introducing a new uplink control channel capability thatenables a mobile terminal to simultaneously report to the radio networkmultiple packet receipt status bits, (e.g., ACK/NACK bits) andchannel-condition bits (e.g., CSI reports). In some embodiments, thisuplink control channel capability also supports sending uplinkscheduling requests from the UE in addition to transmitting multiplepacket receipt status bits and channel-condition bits. In severalembodiments, if the mobile terminal does not have any channel-conditionbits to report in a given subframe, it may transmit ACK/NACK bits usingan uplink control channel transmission mode that does not allow suchsimultaneous transmission.

In one non-limiting example embodiment, a situation may arise where thetotal number of transmitted packet-receipt status bits andchannel-condition bits that can be reported with satisfactoryperformance is limited. The combined reporting in this embodiment isonly enabled up to a certain number of packet-receipt status bits. Forexample, if the number of packet-receipt status bits to be transmittedis less than or equal to a predetermined number (i.e., a threshold),then packet-receipt status bits and channel-condition bits are reportedsimultaneously over the uplink control channel. On the other hand, ifthe number of packet-receipt status bits to be transmitted exceeds thatnumber, then the channel-condition bits may be dropped, i.e., discarded,and only the transmitted packet receipt status bits are transmitted.

In another non-limiting example embodiment, if the mobile terminalapplies partial “bundling” of the packet-receipt status bits, then thenumber of transmitted packet-receipt status bits corresponds to thenumber of bits after bundling. If channel-condition bits are scheduledfor reporting and the number of available packet-receipt status bits islarger than a predetermined number, then the packet receipt status-bitsare bundled to produce that number of bits or fewer, which are thentransmitted together with the channel-condition bits.

In the discussion that follows, specific details of particularembodiments of the present invention are set forth for purposes ofexplanation and not limitation. It will be appreciated by those skilledin the art that other embodiments may be employed apart from thesespecific details. Furthermore, in some instances detailed descriptionsof well-known methods, nodes, interfaces, circuits, and devices areomitted so as not obscure the description with unnecessary detail. Thoseskilled in the art will appreciate that the functions described may beimplemented in one or in several nodes. Some or all of the functionsdescribed may be implemented using hardware circuitry, such as analogand/or discrete logic gates interconnected to perform a specializedfunction, ASICs, PLAs, etc. Likewise, some or all of the functions maybe implemented using software programs and data in conjunction with oneor more digital microprocessors or general purpose computers. Wherenodes that communicate using the air interface are described, it will beappreciated that those nodes also have suitable radio communicationscircuitry. Moreover, the technology can additionally be considered to beembodied entirely within any form of computer-readable memory, includingnon-transitory embodiments such as solid-state memory, magnetic disk, oroptical disk containing an appropriate set of computer instructions thatwould cause a processor to carry out the techniques described herein.

Hardware implementations may include or encompass, without limitation,digital signal processor (DSP) hardware, a reduced instruction setprocessor, hardware (e.g., digital or analog) circuitry including butnot limited to application specific integrated circuit(s) (ASIC) and/orfield programmable gate array(s) (FPGA(s)), and (where appropriate)state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understoodto comprise one or more processors or one or more controllers, and theterms computer, processor, and controller may be employedinterchangeably. When provided by a computer, processor, or controller,the functions may be provided by a single dedicated computer orprocessor or controller, by a single shared computer or processor orcontroller, or by a plurality of individual computers or processors orcontrollers, some of which may be shared or distributed. Moreover, theterm “processor” or “controller” also refers to other hardware capableof performing such functions and/or executing software, such as theexample hardware recited above.

In the following descriptions of non-limiting examples of the presentinvention, a mobile terminal operating according to the LTEspecifications for TDD is assumed, but the described techniques andtechnology may be applied more generally.

A mobile terminal is configured to report multiple ACK/NACK feedbackbits using an uplink control channel, e.g., PUCCH, and an encodingformat that enables simultaneous transmission of multiple ACK/NACK bitsand CSI bits. This simultaneous transmission of multiple ACK/NACK bitsand CSI bits may include configuration of new PUCCH resources, but notnecessarily. One example of a PUCCH mode that could be used for thistransmission is the PUCCH mode described in a co-pending U.S. patentapplication, filed on the same date as the present application andentitled “Simultaneous transmission of AN and CSI using PUCCH Format 3resources,” the entire contents of which are incorporated herein byreference. A mobile terminal feeds back multiple ACK/NACK bits if it hasto report ACK/NACK bits for multiple subframes and/or for multiplecells. Configuration of the mobile terminal may be performed for exampleusing RRC signaling.

FIG. 11 is a process flow diagram that shows example procedures for amobile terminal in accordance with a first, non-limiting exampleembodiment. As shown at block 1110, the operation of the UE may dependon whether the UE has been configured, e.g., by RRC signaling, toutilize a PUCCH mode that supports simultaneous transmission of ACK/NACKbits and CSI. If not, operation proceeds as illustrated at blocks 1120,1130, and 1140. The UE first determines whether ACK/NACK bits and a CSIreport are both scheduled for transmission in a given subframe, as shownat block 1120. In either case, as shown at blocks 1130 and 1140, theACK/NACK bits are transmitted, using a PUCCH mode that does not supportsimultaneous transmission of ACK/NACK bits. If a CSI report isscheduled, however, this involves dropping, i.e., discarding, the CSIreport and transmitting only the ACK/NACK bits as shown at block 1140.

On the other hand, if the UE is configured to support a PUCCH mode thatsupports simultaneous transmission of CSI reports and ACK/NACK bits, themobile terminal also determines whether ACK/NACK bits and a CSI reportare both scheduled for transmission in a given subframe, as shown atblock 1150, and may still use a configured PUCCH mode that does notallow simultaneous CSI transmission, as shown at blocks 1160, if themobile terminal has no CSI bits to report. But if a mobile terminal hasACK/NACK bits and CSI bits to report in the uplink, then the mobileterminal may use a configured PUCCH mode that enables simultaneoustransmission of multiple ACK/NACK bits and CSI bits. This PUCCH mode mayeven support a scheduling request transmission in addition totransmitting multiple ACK/NACK bits and CSI bits.

The process flow illustrated in FIG. 11 reflects the fact that it may bedesirable to also take into account a situation where the total numberof ACK/NACK and CSI bits that can be reported with satisfactoryperformance may be limited. In that case, combined reporting is enabledonly up to a certain number of ACK/NACK bits. Thus, as shown at block1170, the UE determines whether the number of ACK/NACK bits to betransmitted is less than or equal to a threshold value, L. If so, thenACK/NACK bits and CSI bits are reported simultaneously, using the newPUCCH mode, as shown at block 1180. If the number of ACK/NACK bitsexceeds L, on the other hand, then the CSI bits may be dropped and theACK/NACK bits transmitted, as shown at block 1190, using a configuredPUCCH mode that does not supporting simultaneous CSI transmissions. Thenumber L may be any suitable integer, but one non-limiting example isL=10. If the UE applies partial bundling, then the number of ACK/NACKbits to be transmitted and compared to L is the number of bits afterbundling.

A flow chart in accordance with a second non-limiting example embodimentthat includes bundling is shown in FIG. 12. Most of the flow chart isidentical to that of FIG. 11. However, if multiple ACK/NACK bits and aCSI report are scheduled for transmission, and if the number of ACK/NACKbits for transmission is greater than L, then the mobile terminaldetermines whether ACK/NACK bundling is configured, as shown at block1210. If so, then the ACK/NACK bits are bundled to produce L or fewerbits, as shown at block 1220. These bundled ACK/NACK bits are thentransmitted together with CSI bits. If not, the CSI bits are dropped,and the ACK/NACK bits transmitted using a PUCCH mode that does notsupport simultaneous ACK/NACK and CSI transmission, as shown at block1230.

FIG. 13 is another process flow diagram that illustrates, moregenerally, a method for simultaneous reporting of channel-stateinformation and hybrid-ARQ ACK/NACK information, suitable forimplementation by a mobile terminal. Of course, the illustrated methodshould be understood within the context of mobile terminal processing ingeneral, and in the context of forming and transmitting uplink controlchannel information, more particularly. The pictured method may becarried out as part of the processing carried out by a mobile terminalfor each uplink subframe, for example.

As shown at block 1310, the method begins with determining whetherchannel-state information and hybrid-ARQ ACK/NACK bits corresponding toa plurality of downlink subframes or a plurality of downlink carriers,or both, are scheduled for transmission in a given uplink subframe. Ifnot, then conventional techniques for transmitting only ACK/NACK bitsmay be used, as shown at block 1340. On the other hand, if there is a“collision” between a periodic CSI report and ACK/NACK bits, the methodcontinues with an evaluation of whether the number of the firsthybrid-ARQ ACK/NACK bits is less than or equal to a threshold number, asshown at block 1320. If not, conventional techniques for transmittingonly ACK/NACK bits may be used, in some embodiments. If there are nomore than a threshold number of ACK/NACK bits to transmit, however, thechannel-state information and the hybrid-ARQ ACK/NACK bits aretransmitted, as shown at block 1330, using physical control channelresources of the first uplink subframe.

In some embodiments, where ACK/NACK bundling is employed, the number ofhybrid-ARQ ACK/NACK bits, which is compared to the threshold number,represents the number of ACK/NACK bits after ACK/NACK bundling. Further,in some embodiments the threshold number may vary, depending on thenumber of channel-state information bits scheduled for transmission. Forembodiments where the threshold number is static, a suitable numbermight be 10, for example.

Several variants of the technique illustrated in FIG. 13 are possible.For example, as suggested by the flow diagram of FIG. 12, if the numberof ACK/NACK bits scheduled for transmission is greater than thethreshold, the number of bits may be reduced to a suitable number, e.g.,by employing bundling. The bundled ACK/NACK bits may then be transmittedalong with channel-state information bits, using a control channelformat that supports both.

Any of a number of techniques for encoding the channel-state informationand the hybrid-ARQ ACK/NACK bits can be used. In one embodiment, thehybrid-ARQ ACK/NACK bits are encoded with a first encoder and thechannel-state information bits are encoded using a second encoder. Theencoded and hybrid-ARQ ACK/NACK bits and the encoded channel-stateinformation bits are interleaved before transmission. This approachallows the degree of error protection to be allocated between thehybrid-ARQ ACK/NACK bits and the channel-state information. Becausefaulty ACK/NACK data can cause unnecessary re-transmissions, it may beadvantageous to provide more robust error protection to the hybrid-ARQACK/NACK bits, for example.

FIG. 14 is a process flow illustrating a corresponding technique forhandling uplink control channel that has been generated and transmittedaccording to the methods described above. The method illustrated in FIG.14 might be implemented in a base station, for example, such as an LTEeNodeB. For a given subframe the method begins, as shown at block 1410,with the receiving of an uplink subframe that carries control channelinformation in one or several physical control channel resources. Asshown at block 1420, the base station determines whether a number ofexpected hybrid-ARQ ACK/NACK bits is less than or equal to a thresholdnumber. If so, the base station decodes both channel-state informationand hybrid-ARQ ACK/NACK bits from each physical control channel resourcefor which the number of expected hybrid-ARQ ACK/NACK bits is less thanor equal to the threshold number, as shown at block 1430. Otherwise, thebase station uses conventional techniques to decode only ACK/NACK bitsfrom the physical control channel resource, as shown at block 1440.

In some cases, the threshold number varies, depending on a number ofexpected channel-state information bits. In some embodiments, whereACK/NACK bundling is used, the decoding of the control channelinformation yields bundled hybrid-ARQ ACK/NACK bits, in which case themethod further includes unbundling the bundled hybrid-ARQ ACK/NACK bits.In some systems, it may be the case that not all mobile terminals areconfigured for simultaneous reporting of channel-state information andhybrid-ARQ ACK/NACK information, even where they support the feature.Accordingly, the process pictured in FIG. 11 may be preceded, in someinstances, by a determination that the mobile terminal of interest hasbeen configured, via Radio Resource Control signaling, for simultaneousreporting according to the techniques described herein.

The functions in the flowcharts of FIGS. 11-13 may be implemented usingelectronic data processing circuitry provided in the mobile terminal.Likewise, the functions in the flowchart of FIG. 14 may be implementedusing electronic data processing circuitry provided in a base station.Each mobile terminal and base station, of course, also includes suitableradio circuitry for receiving and transmitting radio signals formattedin accordance with known formats and protocols, e.g., LTE formats andprotocols.

FIG. 15 illustrates features of an example communications node 1500according to several embodiments of the present invention. Although thedetailed configuration, as well as features such as physical size, powerrequirements, etc., will vary, the general characteristics of theelements of communications node 1500 are common to both a wireless basestation and a mobile terminal. Further, both may be adapted to carry outone or several of the techniques described above for encoding andtransmitting ACK/NACK bits and channel-state information or decodingsuch information from a received signal.

Communications node 1500 comprises a transceiver 1520 for communicatingwith mobile terminals (in the case of a base station) or with one ormore base stations (in the case of a mobile terminal) as well as aprocessing circuit 1510 for processing the signals transmitted andreceived by the transceiver 1520. Transceiver 1520 includes atransmitter 1525 coupled to one or more transmit antennas 1528 andreceiver 1530 coupled to one or more receive antennas 1533. The sameantenna(s) 1528 and 1533 may be used for both transmission andreception. Receiver 1530 and transmitter 1525 use known radio processingand signal processing components and techniques, typically according toa particular telecommunications standard such as the 3GPP standards forLTE and/or LTE-Advanced. Because the various details and engineeringtradeoffs associated with the design and implementation of suchcircuitry are well known and are unnecessary to a full understanding ofthe invention, additional details are not shown here.

Processing circuit 1510 comprises one or more processors 1540 coupled toone or more memory devices 1550 that make up a data storage memory 1555and a program storage memory 1560. Processor 1540, identified as CPU1540 in FIG. 15, may be a microprocessor, microcontroller, or digitalsignal processor, in some embodiments. More generally, processingcircuit 1510 may comprise a processor/firmware combination, orspecialized digital hardware, or a combination thereof. Memory 1550 maycomprise one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Again, because the various details and engineeringtradeoffs associated with the design of baseband processing circuitryfor mobile devices and wireless base stations are well known and areunnecessary to a full understanding of the invention, additional detailsare not shown here.

Typical functions of the processing circuit 1510 include modulation andcoding of transmitted signals and the demodulation and decoding ofreceived signals. In several embodiments of the present invention,processing circuit 1510 is adapted, using suitable program code storedin program storage memory 1560, for example, to carry out one of thetechniques described above encoding and transmitting ACK/NACK bits andchannel-state information or decoding such information from a receivedsignal. Of course, it will be appreciated that not all of the steps ofthese techniques are necessarily performed in a single microprocessor oreven in a single module.

FIG. 16 illustrates several functional elements of a mobile terminal1600, adapted to carry out some of the techniques discussed in detailabove. Mobile terminal 1600 includes a processing circuit 1610configured to receive data from a base station, via receiver circuit1615, and to construct a series of uplink subframes for transmission bytransmitter circuit 1620. In several embodiments, processing circuit1610, which may be constructed in the manner described for theprocessing circuits 1510 of FIG. 15, includes a hybrid-ARQ processingunit 1640, which is adapted to determine that first channel-stateinformation (from channel-state measurement unit 1650) and firsthybrid-ARQ ACK/NACK bits corresponding to a plurality of downlinksubframes or a plurality of downlink carriers, or both, are scheduledfor transmission in a first uplink subframe, and to determine whetherthe number of the first hybrid-ARQ ACK/NACK bits is less than or equalto a threshold number. Processing circuit 1610 further includes achannel state measurement unit 1650, which produces channel-stateinformation (CSI) bits based on observations of the radio channel, andan uplink control channel encoding unit 1630, which is adapted to sendboth the first channel-state information and the first hybrid-ARQACK/NACK bits in physical control channel resources of the first uplinksubframe, on a single carrier, in response to determining that thenumber of hybrid-ARQ ACK/NACK bits to be transmitted in the first uplinksubframe is less than or equal to the threshold number. Of course, allof the variants of the techniques described above are equally applicableto mobile terminal 1600 as well.

Without changes to current 3GPP specifications, collisions betweenACK/NACK transmissions and CSI reports will likely lead to dropped CSIreports. The novel techniques described herein enable simultaneoustransmission of multiple ACK/NACK bits and CSI. With the use of thesetechniques, fewer CSI reports are dropped, which improves linkadaptation and increases throughput.

It will be appreciated by the person of skill in the art that variousmodifications may be made to the above described embodiments withoutdeparting from the scope of the present invention. For example, it willbe readily appreciated that although the above embodiments are describedwith reference to parts of a 3GPP network, an embodiment of the presentinvention will also be applicable to like networks, such as a successorof the 3GPP network, having like functional components. Therefore, inparticular, the terms 3GPP and associated or related terms used in theabove description and in the enclosed drawings and any appended claimsnow or in the future are to be interpreted accordingly.

Examples of several embodiments of the present invention have beendescribed in detail above, with reference to the attached illustrationsof specific embodiments. Because it is not possible, of course, todescribe every conceivable combination of components or techniques,those skilled in the art will appreciate that the present invention canbe implemented in other ways than those specifically set forth herein,without departing from essential characteristics of the invention. Thepresent embodiments are thus to be considered in all respects asillustrative and not restrictive.

What is claimed is:
 1. A method in a mobile terminal for simultaneousreporting of channel-state information and hybrid-ARQ ACK/NACKinformation in uplink subframes, the method comprising: determining thatfirst channel-state information and first hybrid-ARQ ACK/NACK bitscorresponding to a plurality of downlink subframes or a plurality ofdownlink carriers, or both, are scheduled for transmission in a firstuplink subframe; determining that the number of the first hybrid-ARQACK/NACK bits is less than or equal to a threshold number; andtransmitting both the first channel-state information and the firsthybrid-ARQ ACK/NACK bits in physical control channel resources of thefirst uplink subframe, on a single carrier, in response to determiningthat the number of hybrid-ARQ ACK/NACK bits to be transmitted in thefirst uplink subframe is less than or equal to the threshold number. 2.The method of claim 1, wherein the number of the first hybrid-ARQACK/NACK bits represents a number of ACK/NACK bits after ACK/NACKbundling.
 3. The method of claim 1, wherein the threshold number dependson the number of first channel-state information bits scheduled fortransmission in the first uplink subframe.
 4. The method of claim 1,further comprising: determining that second channel-state informationand second hybrid-ARQ ACK/NACK bits corresponding to a plurality ofdownlink subframes or a plurality of downlink carriers, or both, arescheduled for transmission in a second uplink subframe; determining thatthe number of the second hybrid-ARQ ACK/NACK bits is not less than orequal to the threshold number; and dropping the second channel-stateinformation and transmitting the second hybrid-ARQ ACK/NACK bits inphysical control channel resources of the second uplink subframe, on asingle carrier, in response to determining that the number of hybrid-ARQACK/NACK bits to be transmitted in the second uplink subframe is notless than or equal to the threshold number.
 5. The method of claim 1,further comprising: determining that second channel-state informationand a second hybrid-ARQ ACK/NACK bits corresponding to a plurality ofdownlink subframes or a plurality of downlink carriers, or both, arescheduled for transmission in a second uplink subframe; determining thatthe number of the second hybrid-ARQ ACK/NACK bits is not less than orequal to the threshold number; bundling the second hybrid-ARQ ACK/NACKbits to produce a number of bundled ACK/NACK bits that is less than orequal to the threshold number, in response to determining that thenumber of hybrid-ARQ ACK/NACK bits to be transmitted in the seconduplink subframe is not less than or equal to the threshold number; andtransmitting both the second channel-state information and the bundledACK/NACK bits in physical control channel resources of the second uplinksubframe, on a single carrier.
 6. The method of claim 1, wherein thethreshold number is
 10. 7. The method of claim 1, wherein the firsthybrid-ARQ ACK/NACK bits and the first channel-state information aretransmitted using a Physical Uplink Control Channel (PUCCH) format 3resource in a Long-Term Evolution (LTE) wireless system.
 8. The methodof claim 1, further comprising, before transmitting both the firstchannel-state information and the first hybrid-ARQ ACK/NACK bits:encoding the hybrid-ARQ ACK/NACK bits using a first encoder andseparately encoding the channel-state information bits using a secondencoder; and interleaving the encoded hybrid-ARQ ACK/NACK bits and theencoded channel-state information bits.
 9. A method in a base stationfor processing received reports of channel-state information andhybrid-ARQ ACK/NACK information, the method comprising: receiving aplurality of uplink subframes, each uplink subframe comprising one ormore physical control channel resources carrying control channelinformation encoded by mobile terminals; for each of one or more of thephysical control channel resources, determining that a number ofexpected hybrid-ARQ ACK/NACK bits is less than or equal to a thresholdnumber; and decoding both channel-state information and hybrid-ARQACK/NACK bits from each physical control channel resource for which thenumber of expected hybrid-ARQ ACK/NACK bits is less than or equal to thethreshold number; and decoding only hybrid-ARQ ACK/NACK bits from eachphysical control channel resource for which the number of expectedhybrid-ARQ ACK/NACK bits is not less than or equal to the thresholdnumber.
 10. The method of claim 9, wherein the threshold number dependson a number of expected channel-state information bits.
 11. The methodof claim 9, further comprising: decoding both channel-state informationand bundled hybrid-ARQ ACK/NACK bits from each physical control channelresource for which the number of expected hybrid-ARQ ACK/NACK bits isnot less than or equal to the threshold number; and unbundling thebundled hybrid-ARQ ACK/NACK bits.
 12. The method of claim 9, wherein thethreshold number is
 10. 13. The method of claim 9, wherein decoding bothchannel-state information and hybrid-ARQ ACK/NACK bits comprises:de-interleaving encoded bits from the physical control channel resource,to obtain encoded hybrid-ARQ ACK/NACK bits and separate encodedchannel-state information bits; and decoding the hybrid-ARQ ACK/NACKbits using a first decoder and separately decoding the channel-stateinformation bits using a second decoder.
 14. The method of claim 9,further comprising first determining that the mobile terminal has beenconfigured, via Radio Resource Control signaling, for simultaneousreporting of channel-state information and hybrid-ARQ ACK/NACKinformation.
 15. A mobile terminal configured for simultaneous reportingof channel-state information and hybrid-ARQ ACK/NACK information inuplink subframes, the mobile terminal comprising a receiver circuit, atransmitter circuit, and a processing circuit, wherein the processingcircuit is adapted to: determine that first channel-state informationand first hybrid-ARQ ACK/NACK bits corresponding to a plurality ofdownlink subframes or a plurality of downlink carriers, or both, arescheduled for transmission in a first uplink subframe; determine thatthe number of the first hybrid-ARQ ACK/NACK bits is less than or equalto a threshold number; and send both the first channel-state informationand the first hybrid-ARQ ACK/NACK bits to a base station, via thetransmitter circuit, in physical control channel resources of the firstuplink subframe, on a single carrier, in response to determining thatthe number of hybrid-ARQ ACK/NACK bits to be transmitted in the firstuplink subframe is less than or equal to the threshold number.
 16. Themobile terminal of claim 15, wherein the number of the first hybrid-ARQACK/NACK bits represents a number of ACK/NACK bits after ACK/NACKbundling.
 17. The mobile terminal of claim 15, wherein the processingcircuit is further adapted to: determine that second channel-stateinformation and second hybrid-ARQ ACK/NACK bits corresponding to aplurality of downlink subframes or a plurality of downlink carriers, orboth, are scheduled for transmission in a second uplink subframe;determine that the number of the second hybrid-ARQ ACK/NACK bits is notless than or equal to the threshold number; and drop the secondchannel-state information and send the second hybrid-ARQ ACK/NACK bitsto the base station, via the transmitter circuit, in physical controlchannel resources of the second uplink subframe, on a single carrier, inresponse to determining that the number of hybrid-ARQ ACK/NACK bits tobe transmitted in the second uplink subframe is not less than or equalto the threshold number.
 18. The mobile terminal of claim 15, whereinthe processing circuit is further adapted to: determine that secondchannel-state information and a second hybrid-ARQ ACK/NACK bitscorresponding to a plurality of downlink subframes or a plurality ofdownlink carriers, or both, are scheduled for transmission in a seconduplink subframe; determine that the number of the second hybrid-ARQACK/NACK bits is not less than or equal to the threshold number; bundlethe second hybrid-ARQ ACK/NACK bits to produce a number of bundledACK/NACK bits that is less than or equal to the threshold number, inresponse to determining that the number of hybrid-ARQ ACK/NACK bits tobe transmitted in the second uplink subframe is not less than or equalto the threshold number; and send both the second channel-stateinformation and the bundled ACK/NACK bits to the base station, via thetransmitter, in physical control channel resources of the second uplinksubframe, on a single carrier.
 19. The mobile terminal of claim 15,wherein the threshold number is
 10. 20. The mobile terminal of claim 15,wherein the first hybrid-ARQ ACK/NACK bits and the first channel-stateinformation are sent using a Physical Uplink Control Channel (PUCCH)format 3 resource in a Long-Term Evolution (LTE) wireless system. 21.The mobile terminal of claim 15, wherein the processing circuit isfurther adapted to, before sending both the first channel-stateinformation and the first hybrid-ARQ ACK/NACK bits to the base station:encode the hybrid-ARQ ACK/NACK bits using a first encoder and separatelyencoding the channel-state information bits using a second encoder; andinterleave the encoded hybrid-ARQ ACK/NACK bits and the encodedchannel-state information bits.
 22. A base station configured to processreceived reports of channel-state information and hybrid-ARQ ACK/NACKinformation, the base station comprising a transmitter circuit, areceiver circuit, and a processing circuit, wherein the processingcircuit is configured to: receive, via the receiver circuit a pluralityof uplink subframes, each uplink subframe comprising one or morephysical control channel resources carrying control channel informationencoded by mobile terminals; determine, for each of one or more of thephysical control channel resources, that a number of expected hybrid-ARQACK/NACK bits is less than or equal to a threshold number; decode bothchannel-state information and hybrid-ARQ ACK/NACK bits from eachphysical control channel resource for which the number of expectedhybrid-ARQ ACK/NACK bits is less than or equal to the threshold number;and decode only hybrid-ARQ ACK/NACK bits from each physical controlchannel resource for which the number of expected hybrid-ARQ ACK/NACKbits is not less than or equal to the threshold number.
 23. The basestation of claim 22, wherein the processing circuit is further adaptedto: decode both channel-state information and bundled hybrid-ARQACK/NACK bits from each physical control channel resource for which thenumber of expected hybrid-ARQ ACK/NACK bits is not less than or equal tothe threshold number; and unbundle the bundled hybrid-ARQ ACK/NACK bits.24. The base station of claim 22, wherein the threshold number is 10.25. The base station of claim 22, wherein the processing circuit isadapted to decode both channel-state information and hybrid-ARQ ACK/NACKbits by: de-interleaving encoded bits from the physical control channelresource, to obtain encoded hybrid-ARQ ACK/NACK bits and separateencoded channel-state information bits; and decoding the hybrid-ARQACK/NACK bits using a first decoder and separately decoding thechannel-state information bits using a second decoder.
 26. A mobileterminal configured for simultaneous reporting of channel-stateinformation and hybrid-ARQ ACK/NACK information in uplink subframes, themobile terminal comprising a receiver circuit, a transmitter circuit,and a processing circuit, the processing circuit comprising: anhybrid-ARQ processing unit adapted to determine that first channel-stateinformation and first hybrid-ARQ ACK/NACK bits corresponding to aplurality of downlink subframes or a plurality of downlink carriers, orboth, are scheduled for transmission in a first uplink subframe, and todetermine that the number of the first hybrid-ARQ ACK/NACK bits is lessthan or equal to a threshold number; and an uplink control channelencoding unit adapted to send both the first channel-state informationand the first hybrid-ARQ ACK/NACK bits in physical control channelresources of the first uplink subframe, on a single carrier, in responseto determining that the number of hybrid-ARQ ACK/NACK bits to betransmitted in the first uplink subframe is less than or equal to thethreshold number.